Palynological studies of some roadside plants under exposure to traffic stress

The diverse pollutants emitted from automobiles can have adverse effects on the health and survival of plants, animals and human beings. Different plant species have been known to possess high potential of absorption, detoxification and tolerance of high levels of pollution. Considering this, the present study was carried out to assess the impact of automobile pollution on palynology of roadside plants. Three species, viz. Cannabis sativa, Cassia fistula and Thevetia peruviana growing along the roadsides of nine sites of Amritsar city under different levels of traffic stress were selected for the study. Pollen viability and pollen size were studied by staining pollen with 2,3,5-triphenyl tetrazolium chloride stain and observed under light microscope. Scanning electron microscope was used to study the changes in morphology of the pollen grains. It was observed that the percentage of pollen viability of three species was inversely proportional to the load of traffic at a particular site. Pollen viability was observed to be minimum (C. sativa—22.58 %; C. fistula—21.30 %; and T. peruviana—6.22 %) for the plants of the three species studied growing at traffic site I, site with heavy traffic load as compared to plants growing at sites with comparatively lesser traffic load. C. sativa growing at traffic site IV showed maximum pollen viability of 79.74 %, while C. fistula and T. peruviana growing at traffic site VIII exhibited maximum pollen viability of 83.32 and 68.78 %, respectively. Pollen size and morphology did not show any significant variation and remained unaffected with the increase in traffic stress.